Chemical type thermometers are well known in the art. These devices rely on the melting point of a temperature sensitive composition in order to indicate temperature. See for example U.S. Pat. No. 3,946,612, incorporated herein by reference, which discloses the use of a binary mixture of ortho-chloronitrobenzene and ortho-bromonitrobenzene which form a solid solution as the temperature sensitive indicting composition.
An improved version of the '612 chemical thermometer is disclosed in U.S. Pat. No. 4,232,552, incorporated herein by reference. The improvement disclosed in the '552 patent includes the discovery that certain dyes or combinations of dyes can cause the temperature indicating composition to change color in a reversible manner when it goes from the solid state to the liquid state, or the liquid state to the solid state.
While the clinical thermometer of the '552 patent relies on supercooling for its operation, the use of a nucleating agent to prevent supercooling is disclosed. The use of nucleating agents in the binary system of the '552 patent is disclosed in the Godsey U.S. Pat. No. 3,980,581, Chada U.S. Pat. Nos. 3,712,141, and 3,956,153, all of which are incorporated herein by reference.
Because the binary mixtures of ortho-chloronitrobeneze and ortho-bromonitrobeneze have a 2.degree. F. melting point range, and it is desired to have a clinical temperature reading in about one minute, it is necessary to offset the actual temperature reading and the indicated temperature of the '612 and '552 clinical devices. Hence, the melting point of the a particular temperature indicating composition is different from that shown for the pocket in which it is located. In the prior art clinical devices of the '612 and '552 patents the offset is minus 0.6.degree. F. For example, where the device of the '612 patent indicates a temperature of 98.6.degree. F., the chemical composition in the pocket labeled 98.6 has an initial melting point temperature of 98.0.degree. F. and melts over the range of 98.0.degree. to 100.0.degree. F. However, the device of the '552 patent operates on a completion of melt reading. Therefore, the composition in the 98.6.degree. F. pocket has a completion of melt temperature of 98.0.degree. F., and melts over the temperature range 96.0.degree. to 98.0.degree. F. The result is that in a water bath the equilibrium temperature which is read is a temperature other than the bath temperature.
While this offset permits a rapid accurate reading for clinical devices for oral temperature indications, it is not adequate for all purposes. If the device of the '612 or '552 patent are used to measure the urine temperature, the result is an inaccurate temperature not only because of the offset used, but because the composition has a two degree melting point range.
The device of the '612 patent which operated on an initiation of melt temperature suffered from a difficulty in reading "partial" melts as being indicative of a temperature of the subject. Depending on the experience and judgment of the user different temperature readings could be obtained for the same actual temperature.
Where drug testing by urinalysis is mandated, it is necessary to confirm that the urine sample is a fresh sample of the individual to be tested. This is accomplished by measuring the temperature of the urine sample within four minutes of the taking of the sample. The temperature of the sample must be between 90.5.degree. and 99.8.degree. F. If it is not, there is reason to believe that the individual being tested may have altered or substituted the specimen. See the Federal Register, Part IV, Vol. 53, N. 69, page 11980, Apr. 11, 1988 incorporated herein by reference. The temperature reading must be a real time temperature. That is, the temperature observed must properly read the actual temperature, and change in response to changes in the urine temperature with time.